Prolactin synthesis has been examined in rat pituitaries from animals of various ages. Under certain conditions, rat pituitaries have been shown to make both prolactin and growth hormone at up to 35% and 5% of total protein synthesis, respectively. This is also reflected in the quantity of mRNA present when assayed in a wheat germ translation system. Future work will entail attempts to purify the prolactin mRNA. Various procedures involving physical separation will be used. Immunoprecipitation of polysomes containing nascent chains of prolactin will also be attempted. Eventually we hope to prepare a copy DNA which can be used as a probe for estrogen induced changes in chromatin function. Work will be carried out in both normal pituitaries and endocrine-dependent pituitary tumors.